Lecture9-Feb+4th-Descriptive+stats

Lecture9-Feb+4th-Descriptive+stats -  

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Unformatted text preview:   Quiz
6
due
Today
before
class
   Exercise
3
will
be
posted
sometime
after
 class.

   Due
date
is
Thursday
the
11th
by
1.40pm
   Next
week:
   Tuesday:
Tutorial/quiz
7
   Thursday:
Tutorial/quiz
8
   Developing
questions
   Avoid
 •  Memory
overloaded
questions
 •  Jargon/technical
terms
 •  Double‐barreled
questions
 •  Emotionally
loaded
questions
 •  Leading
questions
 •  Barnum
statements
   Developing
questions
   Control
for
Response
Bias
(Reverse
Code)!!!
   Choosing
answer’s
options
   Closed
number
of
alternatives
 ▪  Likert
scale
 ▪  Yes/No
 ▪  Frequency
 1 2 3 4 5 Strongly Disagree Disagree No Opinion Agree Strongly Agree   Choosing
answer’s
options
   Open‐ended
:
respondents
are
free
to
give
 answers
in
their
own
way
   More
variability
in
answers
   Less
structure
   A
Priori
versus
Post
Hoc
Knowledge
 ▪  What
are
your
thoughts
about
the
man
in
black?
 ▪  Please
rate
the
following
statements
on
a
scale
from
1
 (strongly
disagree)
to
7
(strongly
disagree)
 ▪  Richard
is
a
good
advisor
 ▪  Richard
knows
a
lot
of
about
the
island
 ▪  Richard
knows
what
lies
in
the
shadow
of
the
statue
   Selecting
how
to
administer
the
survey
   Questionnaires
:
PP
read
and
answer
   Interviews
:
responses
provided
verbally
   Questionnaire
   Self‐administered
 ▪  Inexpensive
and
easy
 ▪  Anonymity
 ▪  Low
response
rate
 ▪  Nonresponse
bias
 ▪  Unrepresentative
sample
 ▪  No
one
to
clarify
   Questionnaire
   Investigator‐administered

 ▪  Can
clarify
questions
 ▪  Perceived
as
less
anonymous
=
more
socially
 desirable
responses
   Interview
   Can
be
face‐to‐face,
by
phone,
or
focus‐ group
   Allows
for
clarification
and
more
in‐depth

 investigation
   However,
 ▪  It
is
time
consuming
and
expensive
 ▪  Interviewer
bias
   Interview
   Structured
   Semi‐structured
   Unstructured
   Self‐report
measure
are
subject
to
bias!!! 
   Response
inaccuracy
 1.  Don’t
know
the
answer
   Response
inaccuracy
 1.  Don’t
know
the
answer
 2.  Fail
to
remember
what

 happened
 ▪  Retrospective
reports
   Response
inaccuracy
 1.  Don’t
know
the
answer
 2.  Fail
to
remember
what

 happened
 ▪  Retrospective
reports
 3.  Cannot
predict
future
 ▪  Prospective
reports
   Response
inaccuracy
 1.  Don’t
know
the
answer
 2.  Fail
to
remember
what

 happened
 ▪  Retrospective
reports
 3.  Cannot
predict
future
 ▪  Prospective
reports
 4.  Know,
but
biased
 Social Desirability Reactivity Response Set   Access
to
thoughts
and
feelings
   Inexpensive
   Flexible
   What
do
we
do
with
the
data
collected?
   Descriptive
statistics
   Overview
of
statistical
approaches
   Measures
of
central
tendency
   Measures
of
variability
   Data
organization
   Graphical
representation
   The
normal
distribution
   Descriptive
statistics
   Ways
to
organize,
summarize,
and
simplify
a
set
 of
data
   Inferential
statistics
   Ways
to
use
the
results
obtained
from
samples
to
 help
make
generalizations
about
populations
   Statistics
terminology
   Statistics
 ▪  A
summary
value
that
describes
a
sample

 ▪  e.g.,
average
score
for
the
sample
   Parameters
 ▪  A
summary
value
that
describes
a
population
 ▪  
e.g.,
average
score
for
the
population
   Describe
sample
characteristics
   Identify
outliers
   Identify
patterns
in
the
data
   Identify
distribution
of
scores
to
assist
in
choosing
 the
right
inferential
stats
test
   Descriptive
statistics
   Overview
of
statistical
approaches
   Measures
of
central
tendency
   Measures
of
variability
   Data
organization
   Graphical
representation
   The
normal
distribution
   Single
scores
that
   represent
the
entire
set
of
data
   Identify
the
center
of
a
distribution
of
a
variable


   Three
measures:
Mean,
Median,
Mode
   Type
to
use
depends
on
the
scale
of
 measurement
   Mean
   Average
of
all
scores
   Median
   middle
score
   relatively
insensitive
to
outliers
   Mode
   Most
frequent
score
   Scores
other
than
the
most

 frequent
not
considered
 18
 20
 21
 23
 23
 24
 26
 26
 26
 28
 29
 29
 30
 31
 78
 33
 34
 35
 39
 40
 45
 46
 47
 52
 53
 78 34.3   Mean
   Use
with
interval
or
ratio
variables
   Median
   Use
with
ordinal,
interval
or
ratio
variables
   Mode
   Use
with
nominal
scales
   Not
a
good
representation
of
the

 other
scales,
but
can
be
used
   Descriptive
statistics
   Overview
of
statistical
approaches
   Measures
of
central
tendency
   Measures
of
variability
   Data
organization
   Graphical
representation
   The
normal
distribution
   Range
   Difference
between
highest
and
 78 lowest
scores
   Simplest
and
least
informative
 measure
of
spread
   Semi‐Interquartile
Range
(SIR)
   Less
sensitive
than
the
range
to
 extreme
scores
   Used
when
you
want
a
simple,

 rough
estimate
of
spread
 78 60   Variance
   Average
squared
deviation
of
 scores
from
the
mean
 ▪  2/n
 = 175.83 = 7.33 Var=∑(Xi‐M) 24   Standard
Deviation
   Square
root
of
the
variance
 ▪  SD
=√
∑(Xi‐M)2/n
 =2.7 1   “…First,
a
main
effect
of
expected
memorability
 was
observed,
specifically

higher
false‐alarm
 rates
for
low
compared
to
high
expected‐ memorability
events
(Low:
M
=
.20,
SD
=
.13;
 High:
M
=
.17,
SD
=
.12),
F
(1,
96)
=
10.22,
p
<
.01,
 ηp2
=
.10...”
 Descriptive Stats Inferential Stats   Descriptive
statistics
   Overview
of
statistical
approaches
   Measures
of
central
tendency
   Measures
of
variability
   Data
organization
   Graphical
representation
   The
normal
distribution
   Scatterplot
   Used
to
represent
data
from
two
variables
 ▪  Either
interval
or
ratio
scale
   The
value
of
one
variable
is
represented
on
the

 x‐axis
and
the
value
of
the
other
on
the
y‐axis
   Each
dot
represents

 the
2
scores
for

 one
participant
   Line
Graph
   Data
represented
by
a
series
of
points
connected
 by
a
line
   On
the
X‐axis:
the
timeline
   On
the
Y‐axis:
the
measure
   Bar
Graph
   Length
of
each
bar
determined
by
value
of
the
 Interval/Ratio
variable
   Width
of
each
bar
has
no
meaning
   Nominal
variable
on
the
x‐axis
   Interval
or
Ratio
variable
on
the
y‐axis
   Histogram
 Histogram
of
Exam
Scores
 40
 35
 Frequency
 30
 25
 Polygon 20
 15
 10
 5
 0
 50
 54
 56
 58
 60
 62
 64
 66
 68
 70
 72
 74
 76
 78
 80
 82
 84
 86
 88
 90
 92
 94
 96
 98
 100
 Score
on
Exam
   Presented
with
sets
of
data.

   You
will
be
asked
to
   Calculate
mean,
median,
mode
   Calculate
range,
variance,
standard
deviation
   Create
table
means
   Create
graphs
   No
hand
calculations

   Use
excel
formulas
to
calculate
and
to
graph
   Choose
graph
appropriate
for
your
data
   If
not
familiar
with
excel
go
to
office
hours!
   This
exercise
will
be
turned‐in
via
DROP‐OFF
 box
   Log
into
smart
site
   Go
to
drop‐box
tab
   Upload
your
file
   Due
date
is
Thursday,
by
1.40p.m.
   Descriptive
statistics
   Overview
of
statistical
approaches
   Measures
of
central
tendency
   Measures
of
variability
   Data
organization
   Graphical
representation
   The
normal
distribution
 Mean Mode Median How to standardize distributions: (Xi-M) SD 68% 95% 99% M=0 SD = 1 ...
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This note was uploaded on 06/21/2011 for the course PSYCHOLOGY Psych 41 taught by Professor Castelli during the Winter '10 term at UC Davis.

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